(read-number): Check whether `default' is nil.

diff --git a/lisp/subr.el b/lisp/subr.el
index 39a9caa3106a36e5d4eb9752e6a6387831140416..81f774bdc68b3bcc6ad0bbf3a2f5bde7c8494e99 100644 (file)
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -1329,7 +1329,8 @@ Optional DEFAULT is a default password to use instead of empty input."
     (while
        (progn
          (let ((str (read-from-minibuffer prompt nil nil nil nil
-                                          (number-to-string default))))
+                                          (and default
+                                               (number-to-string default)))))
            (setq n (cond
                     ((zerop (length str)) default)
                     ((stringp str) (read str)))))